Trim the NEWS entry to the user-visible statement

Review feedback from StanFromIreland: no implementation details (the
BIT_MASK macro name is meaningless to users), no description of how it
was fixed (the diff carries that), and no note about the suppressions
file.

Author: matthiasgoergens

Misc/NEWS.d/next/Library/2026-07-30-12-00-00.gh-issue-148286.Kx7Qm2.rst

@@ -1,7 +1,2 @@
-Fix undefined behaviour in the :mod:`ctypes` bit field accessors. The
-``BIT_MASK``, ``GET_BITFIELD`` and ``SET`` macros in
-``Modules/_ctypes/cfield.c`` shifted negative values left and shifted ones
-into the sign bit of a signed type. The bit manipulation is now done in
-``uint64_t`` and converted back to the field's own type, which removes the
-two ``Modules/_ctypes/cfield.c`` entries from
-``Tools/ubsan/suppressions.txt``.
+Fix undefined behaviour when reading and writing :mod:`ctypes` bit fields of
+a signed type.